package dnsforward import ( "encoding/json" "fmt" "net" "net/http" "strconv" "strings" "github.com/AdguardTeam/dnsproxy/upstream" "github.com/AdguardTeam/golibs/jsonutil" "github.com/AdguardTeam/golibs/log" "github.com/AdguardTeam/golibs/utils" "github.com/miekg/dns" ) func httpError(r *http.Request, w http.ResponseWriter, code int, format string, args ...interface{}) { text := fmt.Sprintf(format, args...) log.Info("DNS: %s %s: %s", r.Method, r.URL, text) http.Error(w, text, code) } type dnsConfigJSON struct { Upstreams []string `json:"upstream_dns"` Bootstraps []string `json:"bootstrap_dns"` ProtectionEnabled bool `json:"protection_enabled"` RateLimit uint32 `json:"ratelimit"` BlockingMode string `json:"blocking_mode"` BlockingIPv4 string `json:"blocking_ipv4"` BlockingIPv6 string `json:"blocking_ipv6"` EDNSCSEnabled bool `json:"edns_cs_enabled"` DNSSECEnabled bool `json:"dnssec_enabled"` DisableIPv6 bool `json:"disable_ipv6"` UpstreamMode string `json:"upstream_mode"` } func (s *Server) handleGetConfig(w http.ResponseWriter, r *http.Request) { resp := dnsConfigJSON{} s.RLock() resp.Upstreams = stringArrayDup(s.conf.UpstreamDNS) resp.Bootstraps = stringArrayDup(s.conf.BootstrapDNS) resp.ProtectionEnabled = s.conf.ProtectionEnabled resp.BlockingMode = s.conf.BlockingMode resp.BlockingIPv4 = s.conf.BlockingIPv4 resp.BlockingIPv6 = s.conf.BlockingIPv6 resp.RateLimit = s.conf.Ratelimit resp.EDNSCSEnabled = s.conf.EnableEDNSClientSubnet resp.DNSSECEnabled = s.conf.EnableDNSSEC resp.DisableIPv6 = s.conf.AAAADisabled if s.conf.FastestAddr { resp.UpstreamMode = "fastest_addr" } else if s.conf.AllServers { resp.UpstreamMode = "parallel" } s.RUnlock() js, err := json.Marshal(resp) if err != nil { httpError(r, w, http.StatusInternalServerError, "json.Marshal: %s", err) return } w.Header().Set("Content-Type", "application/json") _, _ = w.Write(js) } func checkBlockingMode(req dnsConfigJSON) bool { bm := req.BlockingMode if !(bm == "default" || bm == "nxdomain" || bm == "null_ip" || bm == "custom_ip") { return false } if bm == "custom_ip" { ip := net.ParseIP(req.BlockingIPv4) if ip == nil || ip.To4() == nil { return false } ip = net.ParseIP(req.BlockingIPv6) if ip == nil { return false } } return true } // nolint(gocyclo) - we need to check each JSON field separately func (s *Server) handleSetConfig(w http.ResponseWriter, r *http.Request) { req := dnsConfigJSON{} js, err := jsonutil.DecodeObject(&req, r.Body) if err != nil { httpError(r, w, http.StatusBadRequest, "json.Decode: %s", err) return } if js.Exists("upstream_dns") { if len(req.Upstreams) != 0 { err = ValidateUpstreams(req.Upstreams) if err != nil { httpError(r, w, http.StatusBadRequest, "wrong upstreams specification: %s", err) return } } } if js.Exists("bootstrap_dns") { for _, host := range req.Bootstraps { if err := checkPlainDNS(host); err != nil { httpError(r, w, http.StatusBadRequest, "%s can not be used as bootstrap dns cause: %s", host, err) return } } } if js.Exists("blocking_mode") && !checkBlockingMode(req) { httpError(r, w, http.StatusBadRequest, "blocking_mode: incorrect value") return } if js.Exists("upstream_mode") && !(req.UpstreamMode == "" || req.UpstreamMode == "fastest_addr" || req.UpstreamMode == "parallel") { httpError(r, w, http.StatusBadRequest, "upstream_mode: incorrect value") return } restart := false s.Lock() if js.Exists("upstream_dns") { s.conf.UpstreamDNS = req.Upstreams restart = true } if js.Exists("bootstrap_dns") { s.conf.BootstrapDNS = req.Bootstraps restart = true } if js.Exists("protection_enabled") { s.conf.ProtectionEnabled = req.ProtectionEnabled } if js.Exists("blocking_mode") { s.conf.BlockingMode = req.BlockingMode if req.BlockingMode == "custom_ip" { if js.Exists("blocking_ipv4") { s.conf.BlockingIPv4 = req.BlockingIPv4 s.conf.BlockingIPAddrv4 = net.ParseIP(req.BlockingIPv4) } if js.Exists("blocking_ipv6") { s.conf.BlockingIPv6 = req.BlockingIPv6 s.conf.BlockingIPAddrv6 = net.ParseIP(req.BlockingIPv6) } } } if js.Exists("ratelimit") { if s.conf.Ratelimit != req.RateLimit { restart = true } s.conf.Ratelimit = req.RateLimit } if js.Exists("edns_cs_enabled") { s.conf.EnableEDNSClientSubnet = req.EDNSCSEnabled restart = true } if js.Exists("dnssec_enabled") { s.conf.EnableDNSSEC = req.DNSSECEnabled } if js.Exists("disable_ipv6") { s.conf.AAAADisabled = req.DisableIPv6 } if js.Exists("upstream_mode") { s.conf.FastestAddr = false s.conf.AllServers = false switch req.UpstreamMode { case "": // case "parallel": s.conf.AllServers = true case "fastest_addr": s.conf.FastestAddr = true } } s.Unlock() s.conf.ConfigModified() if restart { err = s.Reconfigure(nil) if err != nil { httpError(r, w, http.StatusInternalServerError, "%s", err) return } } } type upstreamJSON struct { Upstreams []string `json:"upstream_dns"` // Upstreams BootstrapDNS []string `json:"bootstrap_dns"` // Bootstrap DNS } // ValidateUpstreams validates each upstream and returns an error if any upstream is invalid or if there are no default upstreams specified func ValidateUpstreams(upstreams []string) error { var defaultUpstreamFound bool for _, u := range upstreams { d, err := validateUpstream(u) if err != nil { return err } // Check this flag until default upstream will not be found if !defaultUpstreamFound { defaultUpstreamFound = d } } // Return error if there are no default upstreams if !defaultUpstreamFound { return fmt.Errorf("no default upstreams specified") } return nil } var protocols = []string{"tls://", "https://", "tcp://", "sdns://"} func validateUpstream(u string) (bool, error) { // Check if user tries to specify upstream for domain u, defaultUpstream, err := separateUpstream(u) if err != nil { return defaultUpstream, err } // The special server address '#' means "use the default servers" if u == "#" && !defaultUpstream { return defaultUpstream, nil } // Check if the upstream has a valid protocol prefix for _, proto := range protocols { if strings.HasPrefix(u, proto) { return defaultUpstream, nil } } // Return error if the upstream contains '://' without any valid protocol if strings.Contains(u, "://") { return defaultUpstream, fmt.Errorf("wrong protocol") } // Check if upstream is valid plain DNS return defaultUpstream, checkPlainDNS(u) } // separateUpstream returns upstream without specified domains and a bool flag that indicates if no domains were specified // error will be returned if upstream per domain specification is invalid func separateUpstream(upstream string) (string, bool, error) { defaultUpstream := true if strings.HasPrefix(upstream, "[/") { defaultUpstream = false // split domains and upstream string domainsAndUpstream := strings.Split(strings.TrimPrefix(upstream, "[/"), "/]") if len(domainsAndUpstream) != 2 { return "", defaultUpstream, fmt.Errorf("wrong DNS upstream per domain specification: %s", upstream) } // split domains list and validate each one for _, host := range strings.Split(domainsAndUpstream[0], "/") { if host != "" { if err := utils.IsValidHostname(host); err != nil { return "", defaultUpstream, err } } } upstream = domainsAndUpstream[1] } return upstream, defaultUpstream, nil } // checkPlainDNS checks if host is plain DNS func checkPlainDNS(upstream string) error { // Check if host is ip without port if net.ParseIP(upstream) != nil { return nil } // Check if host is ip with port ip, port, err := net.SplitHostPort(upstream) if err != nil { return err } if net.ParseIP(ip) == nil { return fmt.Errorf("%s is not a valid IP", ip) } _, err = strconv.ParseInt(port, 0, 64) if err != nil { return fmt.Errorf("%s is not a valid port: %s", port, err) } return nil } func (s *Server) handleTestUpstreamDNS(w http.ResponseWriter, r *http.Request) { req := upstreamJSON{} err := json.NewDecoder(r.Body).Decode(&req) if err != nil { httpError(r, w, http.StatusBadRequest, "Failed to read request body: %s", err) return } if len(req.Upstreams) == 0 { httpError(r, w, http.StatusBadRequest, "No servers specified") return } result := map[string]string{} for _, host := range req.Upstreams { err = checkDNS(host, req.BootstrapDNS) if err != nil { log.Info("%v", err) result[host] = err.Error() } else { result[host] = "OK" } } jsonVal, err := json.Marshal(result) if err != nil { httpError(r, w, http.StatusInternalServerError, "Unable to marshal status json: %s", err) return } w.Header().Set("Content-Type", "application/json") _, err = w.Write(jsonVal) if err != nil { httpError(r, w, http.StatusInternalServerError, "Couldn't write body: %s", err) return } } func checkDNS(input string, bootstrap []string) error { // separate upstream from domains list input, defaultUpstream, err := separateUpstream(input) if err != nil { return fmt.Errorf("wrong upstream format: %s", err) } // No need to check this DNS server if input == "#" || !defaultUpstream { return nil } if _, err := validateUpstream(input); err != nil { return fmt.Errorf("wrong upstream format: %s", err) } if len(bootstrap) == 0 { bootstrap = defaultBootstrap } log.Debug("Checking if DNS %s works...", input) u, err := upstream.AddressToUpstream(input, upstream.Options{Bootstrap: bootstrap, Timeout: DefaultTimeout}) if err != nil { return fmt.Errorf("failed to choose upstream for %s: %s", input, err) } req := dns.Msg{} req.Id = dns.Id() req.RecursionDesired = true req.Question = []dns.Question{ {Name: "google-public-dns-a.google.com.", Qtype: dns.TypeA, Qclass: dns.ClassINET}, } reply, err := u.Exchange(&req) if err != nil { return fmt.Errorf("couldn't communicate with DNS server %s: %s", input, err) } if len(reply.Answer) != 1 { return fmt.Errorf("DNS server %s returned wrong answer", input) } if t, ok := reply.Answer[0].(*dns.A); ok { if !net.IPv4(8, 8, 8, 8).Equal(t.A) { return fmt.Errorf("DNS server %s returned wrong answer: %v", input, t.A) } } log.Debug("DNS %s works OK", input) return nil } // Control flow: // web // -> dnsforward.handleDOH -> dnsforward.ServeHTTP // -> proxy.ServeHTTP -> proxy.handleDNSRequest // -> dnsforward.handleDNSRequest func (s *Server) handleDOH(w http.ResponseWriter, r *http.Request) { if !s.conf.TLSAllowUnencryptedDOH && r.TLS == nil { httpError(r, w, http.StatusNotFound, "Not Found") return } if !s.IsRunning() { httpError(r, w, http.StatusInternalServerError, "DNS server is not running") return } s.ServeHTTP(w, r) } func (s *Server) registerHandlers() { s.conf.HTTPRegister("GET", "/control/dns_info", s.handleGetConfig) s.conf.HTTPRegister("POST", "/control/dns_config", s.handleSetConfig) s.conf.HTTPRegister("POST", "/control/test_upstream_dns", s.handleTestUpstreamDNS) s.conf.HTTPRegister("GET", "/control/access/list", s.handleAccessList) s.conf.HTTPRegister("POST", "/control/access/set", s.handleAccessSet) s.conf.HTTPRegister("", "/dns-query", s.handleDOH) }